This invention relates to systems and methods for cleaning surfaces on hard disks, semiconductor wafers, delicate optics, etc., preferably with an oscillating nozzle cleaning system, preferably dispensing cryogenic, solvent or solvent combination cleaning mediums such as carbon dioxide, and preferably utilizing filtered carbon dioxide.
Articles such as hard disks, semiconductor wafers, delicate optics, etc., often must precisely cleaned in order to remove contaminants, either during or after the process for manufacturing the articles. A variety of cleaning methods have been employed with varying degrees of success. Certain of such methods that have been attempted involve imparting carbon dioxide snow onto the article to be cleaning.
An example of such a conventional system is described in U.S. Pat. No. 5,766,061. As a general/summary description of this system, a conveyor transports a wafer carrying cassette to be cleaned through an enclosure. Jet spray nozzles generate carbon dioxide spray that cleans the cassettes. While methods such as described in this patent provide a certain level of cleaning efficacy, improved methods for cleaning a variety of articles are still very much in demand.
In particular, the inventors of the present invention have determined that contaminants in the source carbon dioxide, particularly hydrocarbons, have limited the utility and/or performance of carbon dioxide-based processes such as carbon dioxide-based cleaning processes, and a need exists for improved filtering of carbon dioxide in such processes.
The present invention relates to systems and methods preferably using filtered carbon dioxide, preferably as a cryogenic cleaning medium for cleaning a surface on an article. A summary of a exemplary preferred embodiment of such a cleaning process is as follows, although it should be noted that the present invention is not limited to such a cleaning process (the cleaning process being exemplary, although it is noted that the present invention is particularly advantageous in such cleaning processes).
An enclosure is provided for maintaining a controlled environment during the cleaning process. The enclosure provides ingress and egress from and to a surrounding environment. A holding chuck is provided that is configured to secure the article to be cleaned. A stage or stage means is mounted on the support structure and the holding chuck is mounted on the stage means in a manner so that movement of the article relative to the support structure is provided within the enclosure on a predetermined path between the ingress and the egress points. A preheater is mounted in a first position adjacent the predetermined path in thermal communication with the surface of the article at the first position. A cryogenic spray nozzle assembly is provided wherein a spray nozzle is mounted in the spray nozzle assembly. The spray nozzle is in communication with the cryogenic cleansing medium for providing a cleaning spray at a second position adjacent the predetermined path so that the cleaning spray impinges on the surface to be cleaned at the second position. A post heater is mounted in a third position adjacent to the predetermined path in thermal communication with the surface of the article at the third position. The cryogenic spray nozzle assembly further includes means for imparting cyclic motion in the spray nozzle so that the cleaning spray is moved bidirectionally relative to the predetermined path.
In another aspect of the present invention, systems and methods are provided for cleaning a surface of an article, wherein a preferred system includes a frame work, a holding means that holds the article with the surface exposed, and means for moving the holding means along a predetermined path. A nozzle having a nozzle axis and a nozzle tip is spaced from and adjacent to the predetermined path for delivering a cleaning spray onto the article surface. Means is mounted between the framework and the nozzle for supporting and driving the nozzle tip through a cyclic motion.
In yet another aspect of the present invention, an oscillating nozzle assembly for use in cryogenic cleaning of a surface of an article that must be cleaned substantially free of contaminants is provided. The oscillating nozzle assembly includes an assembly mounting block, a nozzle mounting block, and means for resiliently connecting the nozzle mounting block to the assembly mounting block. Further, the oscillating nozzle assembly includes an eccentric and a driver connected to the eccentric. In addition, means is provided for mounting the eccentric and the driver between the nozzle mounting block and the assembly mounting block. At least one nozzle is included having a nozzle tip, wherein the nozzle is mounted on the nozzle mounting block so that the driver operates to move the nozzle tip cyclically when the driver is energized.
In yet another aspect of the present invention, the oscillating nozzle assembly for dispensing a cleaning medium toward a surface on an article includes a nozzle, a tip on the nozzle for dispensing the cleaning medium, and means for mounting the nozzle. A nozzle assembly base is included together with means for controllably moving the means for mounting the nozzle relative to the nozzle assembly base in a cyclic pattern having a predetermined frequency and amplitude.
In accordance with preferred embodiments, the cryogenic cleaning medium consists of carbon dioxide that is filtered, preferably with a multi-stage filtering process. As commercial sources of carbon dioxide tend to include undesirable amounts of hydrocarbons (due, at least in part, to the solubility of many hydrocarbons in carbon dioxide), a preferably multi-stage filtering process that removes contaminants such as hydrocarbons is implemented.
In preferred embodiments, the filtering process utilizes one or more of the following: A coalescent-type filter that preferably removes the bulk of the contaminant (typically hydrocarbon); this filter preferably consists of multiple stages, such two to four stages, with three stages used in certain preferred embodiments (three separate filters). A heated/catalytic stage preferably removes contaminants such as hydrocarbons; a high temperature pre-heater preferably is utilized to heat the CO2 to accelerate the catalytic reaction; the temperature range preferably is about 250xc2x0 C.-1000xc2x0 C., with the preferred set point temperature about 500xc2x0 C.; a heated catalytic stage (preferably multi-stage), with a heater used to maintain a constant temperature for the catalytic process (preferred temperature ranges may be as stated previously); a multistage catalytic process preferably is utilized that removes contaminants such as hydrocarbons based on multi-heater/catalyst stages; a multi-stage catalytic process preferably is utilized in order to, for example, ensure a near complete reduction/oxidation of hydrocarbons, with the multistage process helping ensure that the majority of CO2 molecules will be in contact with one or more catalytic surface; Activated and non-activated carbon filters (preferably replaceable) preferably are utilized to extract residual contaminants such as hydrocarbons in the CO2 after the catalytic oxidation; in preferred embodiments, this filter is implemented downstream of the catalytic process, where the amount of hydrocarbon in the CO2 is greatly reduced; as a result, filter replacement will be less frequent; A particle filter, preferably a multistage filtration system, consists of one or more ceramic core particulate filters to remove larger particles (e.g., 0.1 micron and larger), which preferably is followed by an all metal electronic grade filter to remove finer particles (e.g., 0.005-0.1 microns); A chiller preferably is provided to control the quality and the conditions of the CO2 entering the nozzle (for a nozzle-based cleaning process, etc.); the chiller core preferably is electro-polished stainless steel to prevent contamination of the CO2.
Methods in accordance with the present invention relate to processing an article having a surface to be cleaned substantially free of contaminates. The process includes the steps of performing a plurality of pre-cleaning fabrication steps, conducting a cleaning process at a cleaning position using a cleaning spray, and performing a plurality of post-cleaning fabrication steps. The step of conducting a cleaning process includes the steps of transporting the surface to be cleaned to the cleaning position together with positioning the surface to be cleaned proximate to the cleaning spray at the cleaning position. Further, the step of oscillating the cleaning spray at the cleaning position in a predetermined pattern is performed to provide improved cleaning in accordance with the present invention.